Process for the preparation of beta keto aldehydes

ABSTRACT

BETA KETO ALDEHYDES ARE PREPARED BY REACTING A VINYL ESTER OF AN ALIPHATIC FATTY ACID WITH ALUMINUM CHLORIDE IN THE PRESENCE OF A SATURATED ALKANE SOLVENT AT A TEMPERATURE RANGE OF 20 TO 50*C. THE ALKANE SOLVENT IS A MUTUAL SOLVENT FOR BOTH THE ALUMINUM CHLORIDE AND THE VINYL ESTER AND IS INERT TO THE REACTANTS AND TO THE PRODUCTS

United States Patent Olfice is 3,803,242 Patented Apr. 9, 1974 3,803,242 PROCESS FOR THE PREPARATION OF BETA KETO ALDEHYDES Edward S. Rothman, North Hills, and Gordon G. Moore,

Willow Grove, Pa., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Original application May 28, 1970, Ser. No.

41,573. Divided and this application Jan. 12, 1973,

Ser. No. 323,194

Int. Cl. C07e 45/18 US. Cl. 260-595 7 Claims ABSTRACT OF THE DISCLOSURE Beta keto aldehydes are prepared by reacting a vinyl ester of an aliphatic fatty acid with aluminum chloride in the presence of a saturated alkane solvent at a temperature range of 20 to 50 C. The alkane solvent is a mutual solvent for both the aluminum chloride and the vinyl ester and is inert to the reactants and to the products.

chloride catalysis to form beta keto aldehydes in the former instance and beta diketones in the latter instance.

The dicarbonyl compounds of this invention form useful complex salts of the type generally known as chelate compounds when reacted with any of several metals. The metallo-chelates are useful as catalysts. The dicarbonyl compounds are used as scavengers of metallic ions in processes such as ore concentration and separation of constituent metals. For example, the copper chelate derivatives of the diketones formed by the reaction of vinyl stearate with aluminum chloride are soluble in organic solvents and the copper chelates are separable by chromatography in benzene or chloroform solution on inorganic supports.

In general, according to this invention an isopropenyl ester of an aliphatic fatty acid, or alternatively a vinyl ester of an aliphatic fatty acid, is diluted with an inert hydrocarbon diluent and treated with 0.2 to 1.0 moles of anhydrous aluminum chloride at about from room temperature to 45 C., for about half an hour, after which the aluminum chloride is destroyed with aqueous dilute hydrochloric acid, and the products are isolated by solvent extraction. It is often convenient to convert the products to the copper chelates to facilitate the purification of product since the metal chelates are well-crystallized, sharp-melting compounds. Typically, the chelates are distinctly colored, e.g. distearoylmethane and dipalitoylmethane are lilac colored, and formylstearoylmethane is blue-gray.

Side reactions are of no significance under the conditions of the reaction. It is to be emphasized that the diketone products are symmetrical diketones and not the derivatives RCOCH CO=CH obtained by isomerizations previously reported [1. Org. Chem 31, 628(1966)].

. The reaction of the isopropenyl esters is illustrated by the following equation: (1).

The chelate formation is illustrated for distearoyl methane in Equation 2;

0- HESS- I I "Has In our experience the similar reaction of e.g. vinyl stearate gives not only the expected beta keto aldehyde H, but also, distearoylmethane I, see Equation 3.

O H 3[C17H35 4 1 0 6:011:

O 'O i O I CnHzs-CHz-CHO CuHasJl-CHz-CnHn Co 01130110 The advantages of the present invention include the simplicity of the route whereby valuable diketones are obtained in a single step from vinyl and isopropenyl esters, and a process that is generally applicable with enol esters from that of acetic acid (C to that of stearic acid (C without the need of high temperatures or vapor phase conditions.

The following examples illustrate the invention but are not intended to have a limiting elfect on its scope.

EXAMPLE I Distearoylmethane (heptatriacontane -18,30-dione) Isopropenyl stearate, 19 g. (0.06 mole) in 25 ml. of hexane was treated with aluminum chloride, 8.5 g. (0.06 mole) with occasional cooling in a waterbath to keep temperature below 40 C. After stirring 0.5 hr. at 40 C. the mixture was poured into a mixture of dilute hydrochloric acid and methylene chloride to destroy the catalyst and extract the product. After separation of the organic layer and evaporation of the methylene chloride the diketone was crystallized directly from methanol to give white plates M.P. 77.377.8, UV max. (isooctane) 273 mu (E=12000), IR 6.24 (chloroform), NMR 3.54, 5.418. The copper chelate derivative was prepared by mixing hot alcoholic solutions of the diketone and cupric acetate. Crystallization of the lilac-colored crystalline product gave the chelate M.P. l13.2l14.0 C. The chelate may be reconverted to the free diketone by shaking its chloroform solution with dilute aqueous hydrochloric acid and evaporating the chloroform layer.

AlCla 3 EXAMPLE n Dipalmitoylmethane Vinyl palmitate, 145 gram (0.51 mole) dissolved in 400 mls. of olefin-free hexane was heated, portionwise with 85 g. (0.6 mole) of anhydrous aluminum chloride added at such a rate that the evolved heat did not allow the temperature to rise more than about 30 C. The mixture was then refluxed for an hour, cooled, and poured into a mixture of 1 liter of water, 300 ml. of concentrated hydrochloric acid and 1.5 l. of methylene chloride. The methylene chloride layer was separated (methanol assisted in controlling emulsion problems), dried, and the solvent was evaporated. The residue, dissolved in hot ethanol, was treated with hot aqueous cupric acetate in slight access whereupon 120 g. of mixed copper chelates separated and were collected on a filter. Chromatography on magnesium silicate gave via hot benzene elution 50 g. of the lilac colored copper chelate derivative of dipalmitoylmethane M.P. 113-114" C., infrared maxima (in chloroform) at 1405 and 1560 waves per centimeter. Further elution with 1:1 methylene chloride/ether gave the blue colored copper chelate derivative of formylpelmitoylmethane M.P. 106-108 C.

EXAMPLE III In a manner similar to Example I, isopropenyl octanoate was converted to dioctanoyl methane M.P. 20-2l C., UV 274 m (isooctane) (E=11,000), copper chelate derivative, M.P. 110.2110.7 C., IR 1350, 1410, 1458, 1554 cm.- (CHC1 EXAMPLE IV In a manner similar to Example II vinyl laurate was converted to dilaurylmethane; copper chelate, M.P. 107- 109 C.; and to lauroylformylmethane, copper chelate M.P. 100-102 C.

EXAMPLE V In a manner similar to Example II vinyl stearate was converted to distearoylmethane M.P. 72 C. (copper chelate derivative M.P. 114 C.) and stearoylformylmethane M.P. 5860 C. (copper chelate M.P. 128-129 C.).

We claim:

1. A process for the preparation of beta keto aldehydes comprising reacting at a temperature of from 20 to C. in the presence of a saturated alkane solvent, aluminum chloride and a vinyl ester of the formula 0 H Bait-045mm wherein R is an alkyl group from 1 to 17 carbon atoms, said saturated alkane being a mutual solvent for both the aluminum chloride and the vinyl ester and being inert to the reactants and to the product.

2. A process for the preparation of beta keto aldehydes comprising reacting at a temperature of from 20 to 50 C. in the presence of a saturated alkane solvent, aluminum chloride and a vinyl ester selected from the group consisting of vinyl stearate, vinyl palmitate, vinyl laurate, viny loctanoate, vinyl propionate, and vinyl acetate, said saturated alkane being a mutual solvent from both the aluminum chloride and the vinyl ester and being inert to the reactants and to the products.

3. The process of claim 2 in which the viynl ester is vinyl stearate.

4. The process of claim 2 in which the vinyl ester is vinyl palmitate.

5. The process of claim 2 in which the vinyl ester is vinyl laurate.

6. The process of claim 2 in which the vinyl ester is vinyl octanoate.

7. The process of claim 2 in which the vinyl ester is vinyl acetate.

References Cited UNITED STATES PATENTS 3/1946 Boese et a1. 260S86 OTHER REFERENCES Rothman: I. Organic Chemistry, vol. 31 (1966), pp. 628-629. 

